Stable and dynamic fracture behavior of PLA was studied using single-edge-notch-tensile specimens. To examine kinetic effect, the specimen was pin-loaded with a special fixture so that it could split and fly away after the fracture. Nonelastic effect or viscoplastic deformation was also measured using an optical high speed extensometer. For the stable and dynamic process, external work applied to the specimen and its fracture surface were partitioned into Us and Ud, and As and Ad, respectively. Energy release rate Gs for the stable crack growth was determined by Us/As. The kinetic and nonelastic energies were measured and subtracted from Ud to evaluate fracture energy Ef for the dynamic process. Energy release rate Gf was then determined by Ef/Ad. The values of Gd (=Ud/Ad) were also obtained to correlate with G s and Gf, and the results were discussed.